Thread grinding and grinding wheel dressing device



April 26,` 1949. s. WALLACE THREAD GRINDING AND GRINDING WHEEL DRESSING DEVICE 5 Sheets-Sheet 1 INVENTOR. A

STANLEY WALLACE Filed March 8, 1945 ATTORNEY April 26, 1949. 5. ALLACE l 2,468,280

THREAD- GR I AND GRINDING WHEEL DRE NG DEVICE Filed March 8, 1945 5 Sheets-Sheet 2 FIG. 2.6

INVENTOR. STANLEY WALLACE BY v ATTORNEY Aprll 26, 1949. f s, WALLACE 2,468,280

THREAD GRINDING AND GRINDING WHEEL DRESSING DEVICE Filed March 8, 1945 5 Sheets-Sheet 3 FIG. 3

1N V EN TOR.

ATTO R N EV STANLEY WALLACE April 26, 1949. s.' WALLACE 2,468,280

THREAD GRNDING AND NDING' WHEEL DRESSING' D CE Filed March 8, 1945 Nl/ENToR. s EY WALLACE ATTORNEY April 26, 1949. s. WALLACE THREAD GRINDING AND GRINDING WHEEL DRESSING DEVICE 5 Sheets-Sheet 5 Filed March 8, 1945 INVENTOR STANLEY WALLACE :m EN

wa NN ATTORNEY Patented Apr. 26, 1949 UNITED STATES `PATENT OFFICE THREAD GRENDING AND GRINDING WHEEL DRESSING DEVICE 27 Claims.

This invention is concerned with improvements in contour-grinding, thread-grinding and grinding wheel dressing devices.

The device made in accordance with the invention is adapted for use in grinding in an eicient and accurate manner internal and external surfaces of different contours, for example, desired threads, and is equipped with a mechanism for accurately dressing the grinding wheel which may at any time Poe used for grinding the desired surface or fthread.

One of the objects of the invention is concerned with the provision of a grinding and dressing device of the character noted herein, which is adapted for use with machine tools, for example, lathes, Shapers, planers, or the like.

Another object resides in the provision of a dressing device in combination with a grinding mechanism, which dressing device is so constructed and arranged that the grinding wheel may be accurately dressed and its contour maintained without changing or disturbing the work set-up.

Still another object is concerned with the provision of a device for dressing grinding Wheels adapted to produce angular or square, external or internal threads, as well as grinding wheels adapted to produce concave, convex, spherical, irregular o-r tapered surfaces.

Additional objects and features will be brought out in the course of the detailed description which is rendered herein with reference to the accompanying drawings. In these drawings,

Fig. l is a front View of an embodiment of the new grinding and dressing device and associated parts, as seen from the position of the operator;

Fig. 2 illustrates a top fview as seen along the lines-2 2 in Fig. 1, with some parts broken away to show details;

Fig,'3 represents a sectional View of the dressing device taken approximately along lines 3 3 in Fig. l;

Fig. 4 shows a partial end view as seen from the right along'lines ffl-4 in Fig. 1;

Fig. `5 illustrates a sectional view taken approximately aiong lines 5-5 in Figs. 1 and 2;

Figs. 6 and 7 are sections through a dressing guide taken along lines {if-5, 'l-'l in Fig. 3;

Fig. "Sshows in diagrammatic perspective view an embodiment of an adapter for use with certain vdressing devices, for example, devices for dressing grinding Wheels employed in grinding internal threads;

Fig. A9 illustrates the adapter of Fig. 'a in full lines in operative position and in dotted lines in retracted position;

Fig. 10 represents a diagrammatic top `plan View of an example of a dressing device for dressing grinding wheels having a shaped or irregular contour,

Fig. 11 shows a section through the device illustrated in Fig. 10 along lines l l-II thereof;

Fig. 12 is a diagrammatic top plan View of a device for dressing grinding wheels such as are used for grinding so-called Acme threads, having two Hanks or sides which converge into a flat surface; and

Fig. 13 illustrates some of the elements of Fig. 12, partially in section, to explain the operation of the'structure.

The invention is not limited to use in connection with any particular type of machine tool, but is shown for convenience with the compound slide of a lathe. The compound slide may be mounted in conventional manner on a cross-slide. Only part of the compound slide of the lathe is diagrammatically indicated in the drawings. A11 otherparts of the lathe are omitted,

The new device comprises several principal parts which are assembled to form a unitary mechanism. These principal parts include (1) thegrinder mechanism comprising a quill containing a spindle which carries the grinding wheel; (2) a mounting member for the quill and for the motor which operates the spindle; (3) a bracket for adjustably supporting the mounting member (and therewith the grinder mechanism) on the compound slide of the lathe; and (4) the grinding wheel dressing device which is mounted on a frame supported by the quill and radially extending therefrom.

The motor and quill mounting mem-ber I is provided for holding the motor 2 (shown in Fig. 1 in dotted lines), which drives a belt 3 to rotate a shaft or spindle 4 journalled in the quill 5. The grinding wheel 6 is attached to the shaft "l at the left end thereof, as is particularly apparent from Figs. 1-3. These parts constitute the 4-5 grinder mechanism.

upright Wall ll of amounting bracket having a 3 base i2 and side walls I3. The base I2 may be adjustably mounted on the compound slide of the lathe. The adjustment of the holder 23 and parts attached thereto is secured by the nut III. The motor-quill mounting member I can thus be placed in a desired position vertically and can be adjusted angularly in any Vertical position thereof. These parts constitute the mounting for the grinder mechanism. The quill and therewith the grinding wheel are therefore adjustable vertically and angularly in a Vertical plane.

The angular adjustment of the mounting -member I holding the motor-quill assembly permits setting Iof the grinding wheel l to the helix angle of the thread to be ground. The elevator Screw I4 permits vertical adjustment of the Iassembly for the purpose of positioning the grinding wheel 6 with respect to the work piece.

The base I2 of the mounting bracket on the upright wall of which the motor-quill assembly is'adjustably secured, as described above, is angularly adjustably mounted on an index :plate I5 hy means of a screw Iii which engages `a nut I1 disposed -in the lower .part of the slot in the compound slide I8. An extension I9 (Fig. i) depending from the index plate I5 engages the upper part of the slot in the compound slide. The index 'plate i5 is thus fixed on the compound slide, and the base I2 of the bracket is held therevon in a position which is angularly adjustable in a horizontal plane.

The compound slide IS is disposed at an `angle with respect to the cross-slide of the lathe, as shown in Figs. 1, 2 and 4. Fig. 4 also shows the gib screws of the compound slide without, however, identifying them by reference numerals.

The understanding of the structure, use iand operation of the device will be facilitated if the following features appearing from :the above genera-1 description are kept in mind: (l) the compound slide lil is adjustable in a horizontal plane at a desired angle to the cross-slide, in order to permit feeding the grinding wheel E with respect to the work-piece on `a line which is subs-tantially in parallel wit-h the flank or side of the thread to'loe produced. This adjustment tends toward economy and accuracy of the 4thread-grinding operation; (2) the mounting bracket carrying on its upright extension Il the motor-quill assembly is :angularly adjustable on the compound slide in a. horizontal plane. in order to compensate for :the angular setting of the compound slide with respect to the cross-slide, permitting also additional angular setting of the entire mechanism for the purpose of placing the quill and associated parts so as to clear the tail stock yof the lathe; (3) the grinding wheel assembly may be vertically moved to an adjusted position in which the point of contact on the grinding wheel is properly aligned with the center of the workpiece; and (4) `the assembly may be angularly tilted in a vertical plane, and may be fixed in adjusted position by means of the screw 9 and nut I0, for the purpose of properly placing the grinding wheel to determine the lhelix angle of the thread yto be produced by it.

Attached to the quill 5, near the end which is adjacent the grinding wheel 6 (see yleft hand end Iof Figs. l :and 2) is a frame on which is mounted :the dressing device for the grinding wheel. This device with its associated parts is generally designated in Figs. 1-4 by reference numeral 20.

Structural details will now be explained mainly with reference to Figs. 1-5, taking into account the sequence of setting-up operations required for producing, for example, an external 60 thread on `a plug gage. It should be noted, however, that the sequence of setting-up operati-ons, as explained below, indicates lonly an example, permitting deviations lthat may be required or desired in practice.

The setting-up of the device is initiated by removing from the compound slide IS the usual tool pos-t and inserting in its place, in the slot of the slide, the nut Il. The index plate I5 is next placed on the compound slide with its eX- tension I9 depending into the upper :portion of the slot thereof. The mounting bracket, which may be a lcast structure having the base I2, side walls I3 land upright wall II, is next placed on the plate I5 and is preliminarily clamped into position by means of the screw |15 which is in threaded engagement with the nut I'i. An index tong-ue 2l is provided in a suitable groove in the base I2 of the mounting bracket for :alignment with .the peripheral index markings on the .plate I5.

The upright wall i I of the mounting bracket is provided with a vertically extending elongated slot or opening 2E (Figs. 1 and 5) adapted to accommodate the holder 23 which is slidable therein responsive to actuation of the elevator screw lll. This screw eng-ages a threaded hole on top of `the vertically extending portion II of the mounting bracket :and carries at its lower end la head 24 which is inserted in t.e holder 23 from beneath through an opening 25. It Should be noted that the thickness of the bracket extension li exceeds that of the holder 23. The face of holder 23 is thus slightly recessed with respect to the :plane of the front wall of the bracket extension.

The screw 9 extends through a :transverse opening in the holder 23 into threaded engagement with the post l. Numeral 26 indicates an index tongue projecting from .the holder 23 for alignment with index marks on the periphery 2'! of the flange 8 or the post l. The screw 9 is provided with an enlargement 28 for engagement with the face of holder 23. Accordingly, when the screw 9 is tightened in its threaded hole in the post "l, the post will be rmly clamped to the holder. can thus be secured independent of the vertical adjustment thereof. The latter is effected by rotating :the screw I4 to shift the holder 23 and with it the post 'I vertically within the slot 22 in the mounting bracket to `any desired position therein. After the required langular and vertical adjustments are made, as will be presently described in detail, the assembly is secured in position by tightening the nut I0, thereby clamping the post 'i firmly in `position on the mounting bracket. At this preliminary stage `of the setting-up operation, the post is merely puton the 'bracket extension I I without any but preliminary and approximate attention to its vertical and angular position.

The mounting post l' is now ready to receive the motor-quill mounting member I. This member is attached by slipping it onto the post i', is particularly indicated in Fig. 5. The clamp screw 30 (Figs. 2 and 4) is for this purpose loosened in order to permit proper placement of member I on the post 1. Numeral 3i in Fig. 5 indicates a clamping sleeve by means of which the assembly is secured on the post 1 responsive to tightening of the screw 30. The proper joining of the motorquill member I with the post 'I and attachment The angular adjustment `of the post 7 thereof tolthefpostaareobtainedby the lockfpin- 32v (Fig. 2f),` which extends. from the motor-quill mounting; member: l.` and is accommodated in` a suitable hole in the ange 8. The mounting member If isfnow put inpreliminary approximate angular positionY byloosening the-screw Q'and nut ID, if necessary.,A androtating the assembly and therewith the-post` 1', whereupon the screw Sand nut llzare preliminarilytightened.

Theframe 33 of the dressing device 20 is provided' with a rearward' extension forming a split tubular: holder 3'4 comprising the sections 35-35 and a rearwardly extending bracket 31. The tubular holderis.y slippedonto the left end of the quillg', as seen in` Figs. 1 and 2, with the bracket-v 31 in:` alignment with a boss 38 projecting from thequill. Ay screw 39 isl provided foi` fastening the bracket131' tothe boss 38 and another screw 39a (/Fig; 1).v is: employed for tightening the sections 353l5 of the tubular holder on the quill in the manner of a clamp.v

The-nextstep insetting up the mechanism includes attachment yof the grinding wheel 5 to the spindle 4 bymeans of the nut 40'. Numeral 4.! indicates Suitable washers between which the grinding wheel is clamped on thespindle 4.

The laterally forwardly projecting part of the frame. off the dressing. device comprises the bottom portion 42.2 forming slide surfaces or ways 't3 (Figs. 2 and. 3)f, the rearrnost way or slide surface terminating in. the upward projection M. The extension 33.` forming the previously mentioned split tubularholder 34.is. also provided with an apron.45 disposed below the grinding wheel 6 and with a to-p apron 46 disposed thereabove, the latter. terminating in a dust shield 41.

The dressing frame described above accommodates on its ways 43 a compensating plate 48. This plate is secured in place by means of screws 491-50 extending upwardly through elongated slots 5|.-5-2, respectively, in the ways 43. The compensating plate 48 may thus be laterally shifted onthe ways 43` of the frame and may be secured in any: laterally adjusted position. The forward end; of the. compensating plate may be suitably curved and may be provided with index marks, as shown inF-igs. 1 and 2. This compensating plate serves as an adjustable support for the dressing head and permits lateral setting of the dressing rpoints so as to obtain proper align-- ment with the: grindingA wheel, and angular setting of the dressing head so as to effect positioning of` thefeed line ofthe dressing points perpendicular to the axis of the work-piece.

Thed-ressing head comprises a bottom portion 53 carrying a pivot pinv 54 which extends in pivotal relation into a hole55in the compensating plate 18,l as shown in Fig; 3. The compensating plate 48 is also providedfwith an arcuate slot for receiving thescrewY 5 6;y which is in threaded engagement with the bottom plate 53. The dressing head can thus be adjustedv angularly on the compensating plate` and can be fixed in any angularly adjusted position. An index member 51 projects forwardly from the bottom plate 53 into a position relative to the index marks on` the forward end of the compensating plate 48. The amount of angular adjustment of. the;- dressing head on the compensating plate is thus visually indicated. The bottom wall 12'` ofthe dressing frame is also provided with an arcuate slot for accommodating the screwv 56 in. any langular' position thereof.

The. bottom. plate 53 of the dressing head terminates in a front wall 58 in which is rotatably jcurnalled thegforward end 59 of the. feed screw,

the rear; end or which` is: threadedyas shown atf 1 Numeral 5l in Fig. 3 indicates abearing sleeveTA which is; attached to the screw by` means of a-,pin 62. The forward end 63 of the feed screvvis-pro-4 f videdzwith. calibrations and with a knurled knob;

M. Rotation of this knobcauses rotationoff-the;` screw'andfits threaded extension 60 in an obvious;

The degree of rotation is indicatefil;by;`

manner. the calibrations or index markings` onY the forward portion of the screw relative to a suitable; index mark onthe front wall58.

The threaded portion 60' of the feed screw `is-inthreaded-engagement with the feed nut 6 5,` alsog` shown in Fig. 3; which in turnisattached to the` top plate 66 by means-of the screw 61. Therefore,4 rotation ofthe feed screw causes'shifting ofi thefeed nut and therewithl shiftingof the top plate Sii-relative tofthe base plate 53. The top plate 66# provided with downwardly depending ears lil-1|', one on either side thereof, and these ears.` carry holes; for sliding engagementwith guide posts (iS-E9 shown in Fig. 1. mounted in thefront wall 58 of the base plate 53;` They serve the'purpose ofsecuring the top plate 66 in proper sliding position and of avoiding angular distortion of the sliding motion-that mayotherwise be induced byA rotation of the feed screw.

The top plate 66 is provided near its rearward; endwith a threadedy hole for receiving the screw 12 which holds the dressing guide on the dressing head. The dressing guide is that part of the.y

mechanism which carries means, e. g., diamonds, for abrasive engagement with the grinding wheel'.

. I, This` dressing gui-de is removably mounted on the for supporting` any one of a number of dressing guides that may be required inthe practical use?- cf the device for dressing grinding wheels of `dif-- ferent contours.

It. will be clear from the foregoing explana-- tions that the'dressing head (and with it any.

.1 dressing guide that may be mounted thereon) is pit/totally supported on the compensating plate 48 by means of the pivot 5d, and` that' it can befxed in any angular-adjustable position byv means of theV screw 56. The compensating plate is- 5. mounted laterallyadjustable on the frame by means of screws Ils and 5tlg as previously described, and the dressing headl and with ity the-A dressing guide carrying the dressing pointsm-ay thus be adjusted laterally with respect to, thev grinding wheel.

The dressing guide to be used in the presenty instance, for dressing the grinding wheel 6, Iwhich is adapted to grind a 60-L7 thread',y comprises, as shown in-ligs.l 1-4, 6 and '1, angularly gener. ally V-shaped block having wing-s 14: and- 155. This block is attached to the top plate 5S ofthe dressing head by means of the screw 12a Dowel pins.1,6?1lock the block in predeterminedv angullar position` on the top plate of the dressing head.-

The wings 'M -15y are each provided with a suitable aperture for accommodating the rack shafts 18;-18', respectively. shaft 18 carryingteeth 801 and sha-ft 19 carrying teeth 3l; The angular position of-these rack shafts corresponds to the angley of tliethread to 'oe out. The; dressing guide.:

Thesev posts are` is therefore individual to the particular grinding wheel which is to be dressed.

The rack shafts are reciprocable within their corresponding openings in the wings 714-75 and each carries at its forward end a holder, as indicated at 82-83, respectively, each holder being provided with a suitable dressing point, for example, a diamond point. These holders are adjustably attached to their respective rack shafts by means of clamp screws 84-85.

The mechanism for reciprocating the rack shafts comprises a vertically disposed plunger 85 having a handle 8l. The plunger extends downwardly into a suitable opening in the guide block and is provided with milled grooves forming gear or teeth sections Sil-| separated by an annular space 92. A spring 93 is placed in a central boring within the plunger. This spring tends to move the plunger upwardly. The upper gear section 9D is in operable gear engagement with the teeth on the reciprocable rack shafts 'E8- 319. Angular oscillation of the plunger therefore causes reciprocation of the racks in opposite directions, and therewith reciprocation of the dressing points on the holders 32-83 parallel to the flanks of the grinding wheel.

In order to avoid chattering of the rack shafts and inadvertent displacement thereof, and therewith displacement of the dressing points, incident to vibrations of the machine during the thread-grinding operation, there is provided a locking feature including a stub pin 95 (Figs. 3 and 7) which is initially inserted through an opening sii in the guide block and is held in position in the annular gear space 92 by the shank of the screw '12. This stub pin is therefore normally positioned between and slightly above any two of the teeth in the lower gear section 9i, and thus prevents escape of the plunger upwardly under the pressure of spring 93, and at the same time locks the plunger against inadvertent angular displacement.

Assuming now that the setting-up of the various parts of the device, as previously discussed, has been completed, certain adjustments are made prior to .starting the operation of grinding the 60 thread on the plug gage which 'was assumed to be the work-piece selected for explanatory purposes. These adjustments include the following:

First, the compound slide I8 is set at an angle of 29 with respect to the cross-slide, in which position the compound slide is approximately shown in the drawings. The base l2 of the mounting bracket is next set on the plate l5 at a compensating angle of 29, the angular adjustment being facilitated by the index tongue 2l in coaction with the index markings on the periphery of the plate l5. A further angular adjustment of the mounting bracket may be made if such is required to clear the tail stock of the lathe. The screw l5 is thereupon tightened, securing the mounting bracket in proper angular position on the properly angularly adjusted compound slide. The nut IC! and the screw il, which have been previously preliminarily tightened, may now be loosened in order to effect angular adjustment of the grinder mechanism in a vertical plane, which adjustment is facilitated by coaction of the index tongue 26 relative to the markings on the periphery 2l of the flange 8 of the post 1. As noted before, this angular adjustment aligns the grinding wheel at the helix angle of the thread to be cut. The screw 9 is then tightened in its threaded hole in post 'l (see Fig. 5) to clamp its enlargement 28 against the face of the member 23, thereby securing the post l, and therefore the grinder mechanism, in angularly adjusted position.

The center alignment of the grinding lwheel with respect to the work-piece is then checked and, if necessary, is corrected and properly adjusted by lifting or lowering the grinder assembly, as required, ley means of the elevator screw ld. Upon completing this adjustment, the nut lli is tightened to secure the post 'l and therewith the grinder mechanism in proper vertical position. The coaction of the screw 9 and nut l0 thus permits angular adjustment of the grinder mechanism independent of its vertical setting.

In the event that the angular adjustment of the base i2 of the mounting bracket on the compound slide necessitated only compensation for the angular setting of the compound slide with 'to the cross-slide, there will be no further adjustment required except to set the dressing points in proper alignment with the grinding wheel. This is done, if it should be necessary, hy loosening the screws 49-59 (Figs. l and 3) and then moving the compensating plate 48 laterally with respect to the ways 133, thereby shifting the dressing head and its associated parts, including the dressing guide and the dressing points, with respect to the grinding wheel and into proper alignment therewith. It is assumed, of course, that the dressing head is in zero or neutral angular position relative to the compensating plate. The line of feed of the dressing points is now perpendicular to the axis of the grinding wheel.

if it was, however, initially necessary to adjust the mounting bracket angularly additionally for the purpose of moving the grinder mechanism to clear the tail stock, such additional adjustment displaced the line of feed of the dressing points angularly with respect to the axis of the grinding wheel, and it will therefore be necessary to restore the direction of feed perpendicular to the grinding wheel axis by angular adjustment of the dressing head on the compensating plate. In other words, if it is assumed that the compound slide was set on the cross-slide of the lathe at an angle of 29, the mounting bracket will have to be set on the plate l5 at a compensating angle of 29, and no other special adjustments need be made except, if necessary, as stated above, perhaps lateral shifting of the dressing head on the compensating plate to obtain proper alignment of the dressing points with the grinding wheel. But if the mounting bracket was initially set on the compound slide an additional, say, 5 so that the grinder would clear the tail stock, this additional 5 adjustment displaced the line of feed of the dressing device angularly with respect to the axis' of the grinding wheel and, inasmuch as the line of feed must be perpendicular to the grinding wheel axis, the additional 5 angular setting of the mounting bracket must be compensated for by angular adjustment of the dressing device so that the line of feed of the dressing points will be perpendicular to the axis of the grinding wheel.

This adjustment is made, if required, by loosening the screw 56 (Fig. 3) and rotating the dressing head into proper angular position on the compensating plate 48; The adjustment is facilitated by the index tongue 51 in coaction with the index markings along the front edge of the plate 43.

The feed screw 6I] is now rotated by operating 9 the knob 64 so as to position the dressing points on the holders 82-83 adjacent to but properly spaced from the grinding wheel.

The thread-grinding operation can now begin.` It is, of course, assumed that the grinding wheel hasbeen previously dressed tothe desired contour.

The motor 2 (Fig. 11) is started so as to rotate the spindle d carrying the'grinding wheel The The head stock of thelathe is retractedv and is thrown at the proper point into gear of the lathe guide spindle. The grinding wheel is then advanced into grinding position with respect to the work-piece byv operating the spindle on the compound slide. As previously remarked, the feed is lateral and nearly in parallel with one side ornank of the thread to be produced. The thread-grinding proceeds for the duration of the working stroke under control of the lathe guidespindle. At the end of the working stroke the grinding wheel is retracted from the workpiece for the idler or return stroke, and is advanced again to the work-piece for the next worl ing stroke. The amount of advance is successively adjusted by operating the spindle on the compound slide. The dressing points have been disengagedfrom the grinding wheel by swinging the dressing handle v8l to the right or left, as noted before, and the dressing device is thus ineffective dur-ing the thread-grinding operation and does not interfere with it.

Dressing of the grinding wheel to maintain its proper contour, which is required from time to time, is' initiated by advancing the dressing points toward the-grinding wheel by means of the knob 64%. The plunger-Sii is then depressed to release the locking pin 95 from engagement with the lower gear section @Lan-d is oscillated so as to reciprocate the rack shafts 'F8-'I9 and therewith the dressing points on the holders 8283 with respect to the fianks of the grinding wheel. The amount of abrasivetobe removed by such dressing is adiusted by proper angularsetting of the forward end 63 of the feedscrew with respect to the index on the front `wall 58 of the dressing head. The operation is in -detail asfollows:

The handle ill projecting from the dressing guide block is grippedand slight downward pressure applied to the plunger i36- to overcome the pressure of spring 93, thus moving the plunger downwardly and the lowermost gear teeth !V out of engagement with the stub pin Q5. While the plunger isfheld down it is oscillated by means of the handle 3'! tomove the dressing pointsalternately back and forth along the angles determined by the setting of the rack shafts 'F8-lg, which correspond to the angles of the flanks of the grinding wheel. The dressing points are advanced toward the grinding wheel by operation of the knob t4 of the feed screw to remove more or less abrasive, as may be required. After the grinding wheel has been properly dressed, the handle v8"! is swung to the right or left, the plunger 86 is released and moves upwardly under pressure of the spring 93. The plunger locks in released position by pressure engagement of the stubpin 95 with the teeth of the lower toothed gear section 9i. This locking, as previously explained, prevents inadvertent displacement of the dressing points and chattering of the rack shafts while the mechanism is employed in the thread-grinding operation.

The amount by which the dressing points-are advanced during the dressing operation, which determines the amount of abrasive removedl from 10 the grinding wheel, is noted by the operator-.by checking the angular position ofr the for-ward end 63 of the feed screw with relation to the index mark on the front Wall 58 of the dressinghead.

The grinding wheel is now againl properly dressed, its contour has been restored and the thread-grinding operation can-be resumed; is done vby advancing the wheel to its proper position with relation to the-work-piece bymeans of` the .crossffeed screw ofy the lathe. The advance corresponds to the amount of abrasive which has been removed during the dressing operation. The thread-grinding is then continued under. control of the lathe guide spindle; as described before.

It should bel noted that the dressing of the grinding wheell is accomplished, as explained; without in any way disturbing the work-piece This also applies to the embodiments yet toy be described.

The dressing guide shown in connection with the above described embodiment is suitable` for dressing the contourof a grindingwheeradapted for-grinding anexternal `60" thread; A similarly constructed dressing guide may be used for dressing grinding wheels adaptedY to produce diierent type threads, for example, 59" or 29 threads. Thedifference resides indiiTerent angular position of the rack shaftsin the guide block. If a diiferent grinding wheelis used, the proper dressing guideismounted on the dressing head, which is .simply accomplished by 4first releasing thescrew T2, removing the previously used dressing guide block, andattaching inits-placethe properV guide block. In other words, the dressing head re mains the same for dressing practically alltypes of external angular grinding wheels, but the dressing of. eachA requires attachmenty of a dierent` dressing guide .block provided with reciprocable rack shafts which hold the dressing points at the proper anglesrequired' for-the contour of any givengrinding wheel.

The steps for setting up the device andfor4 ad*- justing it for the grinding off threads ofv different angles, as well as thegr-inding` operation and the wheel-dressing operation, remain the same as discussed.

The contour of the-grindingv wheel 6, as shown in the abovediscussed embodiment, is assumed to be angularly symmetrical; that is, an equal amount of abrasive is symmetrically removed fromeach side of the Awheel to form the grinding contour. Asymmetrical contours may be pro,- duced,l if desired, by proper lateral positioning of thecoinpensating plate 48 on the ways.4'3 ofjthe dressing frame, and/or byproper angular setting of the'dressing head-onthe compensating plate.`

The adapter illustrated in Fig. 8 is employed when it is desired to dress grinding wheels for :producing internal threads.

The adapter comprises a base plate l Iii which may be mounted on the ways 43 ofy the dressing frame discussed in connection with the previous figures and may be attached thereto by the screws 49-50 shown in Figs. 1 and' 3. The threaded opening Hl' in the plate H0 is, for example, engaged by. the screw 5U shown in Figs. l `and 3. The adapter also comprises. a swing frame or bracket rotatably attached to the plateA H0 Aby means of screw H2; thejbrackethaving a portion M3.v extending in parallel with` the pla-ne ofi` the plate H0 and an extension M4@ placed at ,anzangle thereto. The extension: H4- is. provided with. a

li rear wall and ways or slide surfaces and H8 to which may be attached the compensating plate 48, Fig. 3, of a dressing head constructed similarly to the one described in connection with the previous embodiment. Such compensating plate is attached on the ways I I'I-I |8 by means of screws extending from below through the elongated slots I ISI-| which correspond to the slots 5|52 on the ways 43 of the previously described dressing frame. In other words, the swing bracket of this adapter constitutes a lateral extension of the dressing frame and forms ways for the attachment of the dressing head, which are inclined with respect -to the general plane of the mounting of the dressing frame, and therefore inclined toward the grinding wheel. The arcuate slot in the extension I I4 corresponds to the similarly placed arcuate slot in the plate 42 of the previously described embodiment (see Fig. 3). Numeral |2| indicates a feathered pin mounted in a boss |22 for the purpose of locking the swing bracket either in the position shown in Fig. 8, in which the feathered pin |2| is in engagement with a suitable hole in the base plate I I0, or in alternate position shown in dotted lines in Fig. 9, wherein the feathered pin |2| is in engagement with the hole |23 shown in Fig. 3.

The use of the adapter in dressing grinding wheels for producing internal threads may be explained with reference to Fig. 9.

Numeral indicates the mounting part of the dressing frame, |3| the spindle and |32 the grinding Wheel. The swing bracket ||3 with itsy inclined extension I I4 carrying the ways I I-I I3 is shown in full lines in operative position and in dotted lines in retracted position. The dressing mechanism again comprises a dressing head constructed similarly to the one discussed before,-

having a top plate |33 which is movable by means of a feed screw |35 having a knob |35. The I dressing head can thus be moved in a controlled manner with respect to the grinding wheel. Numeral |34 indicates the compensating plate of the structure.

The dressing guide secured on the top plate |33 of the dressing head is also constructed similarly to the one previously discussed. It comprises a generally V-shaped block having the extensions ISI-|38 with their rack shafts |39--I4EI which may be reciprocated by oscillating the plunger |4| by means of the handle M2. The rack shafts carry the dressing members |-|46. The guide is mounted on the dressing head in a similar manner as discussed before, by a screw 83a shown in the block in Fig. 9,L which corresponds to the screw 'I2 of the previous embodiment, and is held in proper angular position by suitably placed dowel pins. The angle of the sides of the grinding wheel determines the dressing guide to be employed. Any one of a number of such guides may be mounted on the dressing head in the manner already discussed.

The stepsinvolved in setting up and using the device illustrated in Figs. 8 and 9 are also similar to the steps previously discussed in connection with grinding external threads and dressing the grinding wheels used therefor. During the thread-grinding operation the swing fixture or bracket is in dotted-line retracted position (Fig.

9) and for the purpose of dressing is first brought into its operative full-line position. AdjustmentsV are made, if required, as previously described. The dressing device is then in proper `position relative to the grinding wheel. lThe dressing of the wheel is accomplished simply by depressing the plunger IiI and oscillating it by means of the handle M2 so as to move the rack shafts It-itil alternately toward and away from the flanks of the grinding wheel. The amount of abrasive to be removed is adjusted', as in the previous embodiment, by rotating the knob |36 so as to operate the feed screw and thereby to advance the dressing guide and the dressing points thereon by an adjusted desired amount which may be noted by indexing the calibrated forward end E35 of the feed screw with relation to a suitable index mark on the front wall lit of the device. The operator keeps a record of the amount of abrasive removed, and upon completing the dressing operation he places the device in its retracted dottedline position and proceeds with the thread-grinding generally as explained before.

As in the previous case, the grinding wheel |32 shown in Fig. 9 has a symmetrical contour. Asymmetrical contours .may be produced, as already discussed, by proper lateral placing of the adapter on the principal dressing frame and by proper shifting of the dressing head on the ways of the adapter frame I ifi. The angular adjustment of the dressing head on the compensating plate may likewise be employed for this purpose.

Figs. l0 and ll show the essential parts of a dressing head and dressing guide for contour dressing.

Numeral |50 designates the top plate of the dressing head corresponding to the top plate 56 of the previously described structure. A feed nut Ibi is attached to the top plate by means of a screw |52, corresponding to the feed nut 65 and screw tl of the previous embodiment. The feed nut is engaged by the feed screw |53 carrying a shoulder journal sleeve H54, in a similar manner as the feed nut 65 is engaged by the feed screw t@ of the rst described structure. A bushing |55 is provided in the left hand end of the top plate |50 for mounting thereon the dressing guide by means of the screw |51 in a similar manner as the dressing guide of the previous embodiment is mounted by means of the screw T2, as shown in Fig. 3. The feed screw |53 projects to the outside of the dressing head and may be rotated by a suitable knob. The dressing guide mounted on the dressing head in Figs. 10 and ll may thus be moved toward and away from the wheel to be dressed, which is diagrammatically shown in Fig. 11 at |14.

The contour dressing guide comprises a base plate lii secured on the top plate of the dressing head by the screw i5?, which is threaded into the bushing |55. The base plate |56 carries a rack, i. e., a strip-like member |59 attached by screws Iliil-Il. This rack strip is provided with gear teeth i5?. Adjacent the gear teeth |62 of the rack is mounted a templet Iii?, having a desired shape, e. g., the shape indicated in Fig. l0. This templet is attached by means of a screw its shown in Fig. ll and is properly aligned in position by two dowel pins M55-|56, shown in Fig. l0. The templet forms the guide for the lateral dressing motion to be imparted to the dressing tool I5?.

The dressing tool or point IS'I is mounted in an axially movable plunger |58 which is slidably secured in a guide block 59 and is prevented from rotating therein by a pin I'I which engages a guide slot Ill provided in the left hand portion of the plunger, as shown. At the right ramasse ihand end o'f the block W9 is provided abushing which isin -threadedlengagement therewith and forms a bearing shoulder for a rotatably mounted actuating member from which projects upwardly the handle |16 and downwardly a 'toothed section |11 forming a gear sector which is in gear mesh engagement with the teeth iii@ on the stationary rackmember |59.

A spring |80 is disposed within the block |69 iin the space between the bushing and the 'shoulder formed by the left hand portion of the 'plunger |68. This spring moves the plunger and "the dressing point |61 attached thereto in left hand direction toward the grinding wheel Elfi vwhich is to be dressed. At-its right hand end, whichproi'ects from the bushing titi, the plunger Acarries a guide or follower ll, the lower angula'rly disposed point of which is in Contact with ithe shaped edge of the templet |63. The follower is secured by means of a screw i853.

'I'he guide block |69 is 'mounted-on a bar l|i2 which is secured to the plate |56 by screws i-i 81. The alignment of thefassembly is securedby gib'means, including `gib screws one of which is shown in Fig. ll at v|83. The bar |82 thus forms a lateral slide base 'engaged by ways in the guide block |69.

The operation of the above described contour grinding anddressing structure is as follows:

lThedressing point I 61 is advanced to the worlt piece, i. e., to the grinding'wheel lli by rotating the feed screw |53. The amount of advance f may be noted by the operator by observing suitable index markings on the feed screw with relaftio'n to an index line at the front of the dressing i Ehead. The handle |15 is then oscillated, thereby rotating the toothed gear sector |11 which is in gear mesh engagement with the teeth of the staytionary rack |52. The dressing guide, including the block |69, and all parts attached thereto move sideways, in a lateral reciprocating motion, inresponse to the oscillating actuation of the handle, the movement being along the slide bar |82 on the base plate |56. The axially movable plunger |68 is moved toward the wheel. |14 by `the spring |89, but in the ycourse of the sideways fmovement will be actuated to move in axial di- -rection in accordance with the shape of the templet |63 which is in engagement with the point 'of the follower IBI. The axial displacement of 'the'dressing point |51, during its lateral recipro- `leating motion, is thus a function of and in `accordance with the shape determined by the 'templet The follower traces the contour of the Ytemplet and therefore determines the corresponding contour of the grinding wheel VM.

The contour dressing guide is shown Figs. 10 and 11 in a position perpendicular to the axis of the grinding wheel. If desired, the guide may be positioned on the dressing head at an angle to the wheel. This is done by rst shift- 'ingthe block |69 sideways, to gain access to the screw |51, then loosening this screw, rotating the guide into the proper desired angular position, and again tightening the screw |51. The "degree of angular adjustment may be determined "by displacement of the guide with respect to the index markings on the plate |99 shown in Fig. l0, which is attached to the top plate |50 of the dressfing head by means of the screws lill-|92. Angu- -'-larp1acement may also be obtained by suitable adjustment of the device on a compensating plate such as the plate 48, Figs. 1, 2, 3 of the i'lrst described structure.

It-isunderstood, of course, that any'given shape laterally siidabiy embodiments.

tubular screw v2 |14.

to be ground or dressed requiresa correspondingly `shaped templet. -By using-different templets lit 'the contour guide into-a desired angular position, as previously discussed, the sides of the grinding wheel may be dressed, permitting the `grinding of stepped'or-offset surfaces, angular surfaces, and surfaces with intricate outlines.

In Fig. 12 is^'shown afdressing device `having three dressing points indicated at 200, 2ll| and 232. Some of theelements of this device are Vin i, dicated separately'in Fig-13. The dressing points 23|) and 202, as 'shown inFig. l2, are mounted'in rack shafts indicated at-203 and-204, respectively, which may be reciprocated by means of the handle Elli adapted to oscillate the plunger 206 `in a similar manner as alreadyfdiscussed in connection with the corresponding plunger of previous The rack shafts-203 and 4264 are movably mounted-in the win-gs2|l1and`208,lre spectively, of the guide-block. The arrangement is thus similar to Athose already described, except that the dressing pointsZDll, 2132 are mounted for displacement at a diferentangle--in this particular case, atan angle of approximately 29.

The third dressing kpoint 528|, as indicated in Figs. i2 and13, is mounted on airnember .2 lo and is secured in position thereon by va screw 2||. This member is secured for-axial sliding displacement in the arm -2|2 andfextends through the The member Av2li!) maybe axially shifted by rotating the tubular 'screw 2id which extends through a threaded -hole v-in the arm 2|3. The rotation of member y2| is prevented by a screw 2|6 engaging'a threaded hole in the arm Y2|2 and projecting a pin-like extension into the slotl220. The structure and operation will be understood when itis-considered that the mem-ber 2| 0 is-made in the form of a shaft extending at the left end-slidably through the arm .2|2 and at lthe right end through the hollow tubular screw 2|4, into sleeve-like coupling engagement with the screw. Accordingly,

when the feed screw is rotated, it is displaced axially within its thread in the arm 2|3 and the shaft 2|E| is likewise axially displaced within the arm 2|2. The feed screw may also extend into the shaft 2li), and may carry a sleeve nut which is in splined engagement with the shaft. VAny other suitable 'arrangement for obtaining axial displacement of the shaft 2||J by rotation of the feed screw may be adopted.

rThe above described structure may be employed for dressing wheels used in a 29 so-called Acme thread. The flanks of the grinding wheel 22| are in this instance dressed by angularly reciprocating the dressing points '20c and 202 in the manner already described, by operating the handle 2535 to oscillate the plunger 206; and the edge of the grinding wheel .22| is dressed by actuating the knobI 2| 5 to 'rotate the screw 2M which in turn causes axial displacement of the spindle or shaft member 2|0 and therewith of thedressing point 20| securedthereto.

Dressing guides constructed similarly to the one described in connection with 12 may also be provided yfor dressing wheels used 'in grinding square threads. The 'dressing points 20) and 292 wouldin'such-case beimountedifor parallel vreciprocationl in planes perpendicular 4'to 'the axis zof the grinding wheel vand fthe third dressings point :20| "wouldbe provided forreciprm ation in parallel with the axis of the grinding wheel substantially in the same manner as indicated in Fig. 12.

The dressing guides shown in Figs. 10, il and 12 may be mounted on identical dressing heads, e. g., o-n the dressing head discussed in connection with the embodiment `shown in Figs. l to 5, inclusive. Dressing guides for irregular or shaped contours in connection with grinding wheels for internal threads or surfaces may be mounted on dressing heads carried by the swing bracket or swing fixture discus-sed in connection with Figs. 8 and 9.

Changes may be made within the scope of the following claims wherein I have defined what is considered new and desired to have protected by Letters Patent of the United States.

I claim:

1. In a thread-grinding device `for use with a lathe or the like, having a bracket for attachment to the compound slide oi' such lathe and -means for adjustably holding on said bracket a mounting including a quill containing the spindle carrying at one end thereof a suitable grinding wheel for grinding contact with the work-piece on said lathe and also including driving means for said spindle, a device for dressing said grinding wheel comprising a frame projecting from said mounting radially of said quill, Ways formed on said frame extending substantially parallel with the axis of said quill, a dressing head mounted on said ways in adjustable position relative theren to, means for adjusting said dressing head angularly, and a dressing guide attached to said dressing head and carrying means for dressing said grinding Wheel.

2. The combination and structure defined in claim l, wherein said frame is removably attached to said mounting adjacent the grinding wheel secured to the spindle extending irom the end of said quill.

3. The combination and structure dened in claim l, wherein said frame is removably attached to said mounting adjacent the grinding wheel secured to the spindle extending from the end o'f said quill, together with means for angularly adjusting said dressing head for the purpose of disposing the dressing means thereon angularly with respect to the grinding surface of said grinding wheel.

4. The combination and structure dened in claim l, 'wherein said frame is removably attached to said mounting adjacent fthe grinding wheel secured to the spindle extending from the end of said quill, said frame projecting forwardly With the ways thereon disposed in a plane extending substantially horizontally in parallel with the axis of said grinding wheel but radially spaced therefrom.

5. The combination and structure defined in claim l, wherein said dressing guide comprises a member which is axially reciprocable, a toothed rack carried by said member, a plunger carrying vgear means engaging said rack teeth, means for angularly oscillating said plunger to reciprocate said member, and a dressing point carried by said member for dressing engagement with said grinding wheel,

6. The combination and structure defined in claim 1, wherein said dressing guide comprises an axially reciprocable member disposed at a xed angle bearing a predetermined relation to the angle of the thread to be produced, a toothed rack carried by said member, a plunger carrying gear means for engagement with said rack teeth,

means for angularly oscillating said plunger to' reciprocate said member, a dressing point carried by said member for dressing engagement with said grinding wheel, and means for locking said plunger against accidental angular displacement incident ot vibrations caused by the threadgrinding operation of the device.

7. The combination and structure defined in claim l, wherein said dressing guide comprises a plurality of axially reciprocable members disposed at angles corresponding substantially to the anges of the Ilanks of 'the thread to be produced, gear means on said members, a plunger carrying a gear for engagement with the gear means cn said members, means for oscillating said plunger to reciprocate said members for the purpose of moving the dressing means thereon with respect to said grinding wheel, and means normally engaging the gear on said plunger to lock said plunger against inadvertent displacement.

8. The combination and structure defined in claim l, especially for producing threads by employing grinding wheels rraving three distinct grinding surfaces, wherein said dressing guide comprises a pair oi members adapted for axial displacement and a third member adapted for displacement yat an angle thereto, and means for reciprocating said members including a rotatable plunger for oscillating said pair of members and a separate shaft for displacing said third member.

9. The combination and structure defined in claim l, especially for grinding internal threads, wherein said dressing head is mounted on ways formed on a bracket removably secured to the Ways formed on said frame.

l0. The combination and structure defined in claim l, especially for producing internal threads, wherein said dressing device comprises a plate adapted for mounting on the ways of said frame, and a bracket rotatably mounted on said plate and forming ways for receiving said dressing head.

il. The combination and structure defined in claim l, wherein a plate is laterally adjustably secured on the ways of said frame, together with means for pivotally mounting said dressing head on said plate.

l2. A device for dressing grinding wheels having three grinding surfaces to maintain the contours thereof, two of such surf-aces forming the flanks and one of the surfaces forming the edge of the grinding wheel, said device comprising a frame, a dressing head mounted on said frame in laterally and angularly adjustable position relative thereto, and a dressing guide mounted on said dressing head, said dressing guide comprising a pair of axially movable members carrying dressing points for dressing engagement with the flanks of said grinding Wheel and an axially movable member carrying a dressing point for dressing engagement with fthe edge thereof, a common plunger for reciprocating said pair of members, and a separate shaft for reciprocating the member carrying the dressing point for the edge of said grinding Wheel.

13. A device for dressing grinding wheels employed for grinding internal surfaces, said device comprising a frame having means forming a mounting base, a plate adjustably secured to said base, a bracket rotatably secured on said plate, a dressing head carried by said bracket, a dressing guide carried by said dressing head, dressing means carried by said dressing guide, and means for reciprocating said dressing means.

14. A device for dressing grinding., wheels employed for grinding internal` surfaces, said device comprising a frame having means forming a mounting base, a plate adjustably secured on said base, a bracket rotatably secured on said plate, a dressing head secured to said bracket, a dressing guide, carried by said dressing head, said bracket being adapted for disposing said dressing head and guide secured thereto in disengaged position with the dressing means out of contact with said grinding wheel and radially spaced therefrom and alternately in working position with the dressing means disposed substantially perpendicular to the grinding wheel and adjacent the circumference thereof.

15.A A device for dressing grinding wheels employed for producing shaped surfaces, said device comprising a frame, a dressing head mounted on said frame in laterally and angularly adjustable position relative thereto, a dressing guide mounted on said dressing head, said dressing guide comprising an axially and laterally movablev plunger carrying dressing means at one endl thereof for dressing engagement with the grinding wheel, means for holding the plunger elastically in normal position, a templet removaby attached rto said dressing guide and having a shape corresponding to the shape of the grinding wheel to be dressed, a follower attached to said plunger and contacting said templet, and means for displacing said plunger in accordance with the shape of said templet.

16. A device for use in dressing a grinding wheel to maintain its contour comprising a dressing guide having a pair of axially movable members each carrying a dressing point at the end thereof for dressing engagement with the iianks of the grinding wheel, gear teeth alongside each of said members, a. plunger disposed perpendicular to said members and carrying a gear for meshing with the gear teeth on said members, an annular groove in the gear on said plunger, a locking member projecting into said groove, and means for normally holding said locking member in engagement with gear teeth on said plunger for the purpose of preventing accidential displacement thereof.

17. The combination and structure defined in claim 16, wherein a pin-like member constitutes said locking member, and spring means acting on said plunger for holding said pin in engagement with said gear at one side of said annular groove.

18. In combination with thread-grinding apparatus for use with a lathe or the like including a bracket adapted to be angularly adjustably attached to the compound slide of such lathe and having an adjustably secured mounting member for holding a quill carrying a grinding wheel, a device for dressing said grinding wheel, comprising a frame, means for securing said frame on said quill in radially projecting relation rela-- tive thereto, wheel dressing means carried on said frame, and means for angularly adjusting said wheel dressing means to compensate for the angular adjustment of said bracket on said cornpound slide.

19. The structure and combination defined in claim 18, wherein the means for adjustably securing said mounting member comprises a holder disposed in a slot in said bracket, a screw for securing said mounting member on said holder in angularly adjustable position relative thereto,

I8. means `for vertically adjusting said holder and said mounting member thereon, and means including said holder for attaching said mounting member in firm engagement with said bracket.

20. The structure and combination dened' claim 18, together with means for selectively positioning said wheeldressing means in oper-ative position perpendicular to the axis of saidgrinding wheel and alternatively in non-operative position in a plane extending substantially in parallel with the axis of said grinding Wheel.

21. Grinding apparatus for use with a lathe, comprising a bracket for attachment to the compound slide of a lathe and adjustable thereon in` a horizontal plane, a mounting member secured to said bracket and adjustable thereonv in' a vertical plane, a quill carriedv by said mounting member and carrying a spindle supporting a1 grinding wheel, a frame secured to said qui1l,.and a wheel dressing device secured to said frame, said wheel dressing device being adjustable in. parallel with the axis of said grinding wheel and. at arr angle to the axis thereof.

22. The structure and combination defined in claim 21, together with index means for indicating the adjustment of said. bracket on. saidmachinel tool, index means for indicating the adjustment of said mounting member on said bracket, and index means for indicating the adjustment of said wheel dressing device on said frame.

23. In combination, a tubular member for rotatably mounting a grinding wheel axially projecting therefrom at one end thereof, a frame secured to said tubular member and radially projecting therefrom adjacent said grinding wheel, means on said frame forming laterally directed Ways thereon, a dressing head disposed on said ways, a top plate forming part of said dressing head, means for adjusting the position of said top plate, a dressing guide mounted on said dressing head, a holder axially movably disposed in said dressing guide, said holder carrying a dressing member for engagement with said grinding wheel, a toothed member associated with said dressing guide, and a handle for moving said toothed member to displace said holder for moving said dressing member relative to said grinding wheel.

24. In combination, a tubular member for rotatably mounting a grinding wheel axially projecting therefrom at one end thereof; a frame secured to said tubular member and radially projecting therefrom adjacent said grinding wheel, means on said frame forming laterally directed ways thereon, a dressing head disposed on said ways, a top plate forming part of said dressing head, means for adjusting the position of said top plate, a dressing guide mounted on said dressing head, -a holder axially movably disposed in said dressing guide, said holder carrying a dressing member for engagement with said grinding wheel, a toothed member associated with said dressing guide, and a handle for moving said toothed member to displace said holder for moving said dressing member relative to said grinding wheel over a predetermined path which corresponds to the configuration of the surface of the grinding wheel which is to be dressed by said dressing member.

25. In a device for dressing a cgrinding wheel, a dressing member, a holder for carrying said dressing member, a guide for axially movably mounting said holder, a toothed member associated with said guide, handle means for moving said toothed member to displace said holder and the dressing member carried thereby, a dressing head carrying 19 a top plate, means for adjustably'mounting said guide on said top plate, means for adjusting the position of said top plate, and means for adjustably mounting said dressing head carrying said top plate.

26. The structure and combination dened in claim 25, together with a frame for receiving said means for adjustabl;T mounting said dressing head carrying said top plate, mounting means for said frame, and means for adjustably securing said mounting means.

27. In a thread-grinding apparatus for use with a lathe or the like, having a bracket for attachment to the compound slide of such lathe and means for adjustably holding on said bracket a mounting including a quill containing the spindle carrying at one end thereof a suitable grinding Wheel for grinding contact with the Work-piece on said lathe and also having driving means for said spindle, a device for dressing said grinding wheel comprising a frame, means for securing said frame on said quill, a compensating plate adjustably mounted on said frame, a dressing head kadjustably mounted on said compensating plate, a dressing guide secured to said dressing head and carrying means for dressing said grind- 20 ing wheel, index means on said bracket for adjusting said bracket angularly on said compound slide, and index means on said dressing head for adjusting the angular position thereof on said compensating plate.

STANLEY WALLACE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,259,131 Ritz, Jr Mar. 12, 1918 1,350,044 Stryhal Aug. 17, 1920 1,355,710 Stryhal Oct. 12, 1920 1,369,789 Dawson Mar. 1, 1921 1,412,778 Cumner et al Apr. 11, 1922 1,424,765 Larrson Aug. 8, 1922 1,468,357 Cumner et al Sept. 18, 1923 1,479,116 Tozer Jan. 1, 1924 1,527,295 Cumner et al Feb. 24, 1925 1,719,689 Buehrle July 2, 1929 2,218,775 Turrettini Oct. 22, 1940 2,392,332 Mahlmeister Jan. 8, 1946 

